Fortran and FTG interface update

compare.py:

• Added tolerance file to set tolerance by field
• Format error in scientific notation
• If field is NaN in both savepoint, it will no longer raise an error

FTG:

• Reallocate
• Update to the new Fortran interface (possibility of perturbation)

Fortran interface:

• Combine fs_read_and_perturb into fs_read interface with optional argument